Ventilation mask with integrated piloted exhalation valve

ABSTRACT

A mask for achieving positive pressure mechanical ventilation (inclusive of CPAP, ventilator support, critical care ventilation, emergency applications), and a method for a operating a ventilation system including such mask. The mask includes a piloted exhalation valve that is used to achieve the target pressures/flows to the patient. The pilot for the valve may be pneumatic and driven from the gas supply tubing from the ventilator. The pilot may also be a preset pressure derived in the mask, a separate pneumatic line from the ventilator, or an electro-mechanical control. The mask of the present invention may further include a heat and moisture exchanger (HME) which is integrated therein.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/411,348 entitled VENTILATION MASK WITH INTEGRATED PILOTEDEXHALATION VALVE filed Mar. 2, 2012, which claims priority to U.S.Provisional Patent Application Ser. No. 61/499,950 entitled VENTILATIONMASK WITH INTEGRATED PILOTED EXHALATION VALVE filed Jun. 22, 2011, andU.S. Provisional Patent Application Ser. No. 61/512,750 entitledVENTILATION MASK WITH INTEGRATED PILOTED EXHALATION VALVE AND METHOD OFVENTILATING A PATIENT USING THE SAME filed Jul. 28, 2011, thedisclosures of which are incorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to systems and methods for controllingdelivery of a pressurized flow of breathable gas to a patient and, moreparticularly, to a ventilation mask such as a full face mask, nasalmask, nasal prongs mask or nasal pillows mask for use in critical careventilation, respiratory insufficiency or OSA (obstructive sleep apnea)with CPAP (Continuous Positive Airway Pressure) therapy andincorporating a piloted exhalation valve inside the mask.

2. Description of the Related Art

As is known in the medical arts, mechanical ventilators comprise medicaldevices that either perform or supplement breathing for patients. Earlyventilators, such as the “iron lung”, created negative pressure aroundthe patient's chest to cause a flow of ambient air through the patient'snose and/or mouth into their lungs. However, the vast majority ofcontemporary ventilators instead use positive pressure to deliver gas tothe patient's lungs via a patient circuit between the ventilator and thepatient. The patient circuit typically consists of one or two large boretubes (e.g., from 22 mm ID for adults to 8 mm ID for pediatric) thatinterface to the ventilator on one end, and a patient mask on the otherend. Most often, the patient mask is not provided as part of theventilator system, and a wide variety of patient masks can be used withany ventilator. The interfaces between the ventilator, patient circuitand patient masks are standardized as generic conical connectors, thesize and shape of which are specified by regulatory bodies (e.g., ISO5356-1 or similar standards).

Current ventilators are designed to support either “vented” or “leak”circuits, or “non-vented” or “non-leak” circuits. In vented circuits,the mask or patient interface is provided with an intentional leak,usually in the form of a plurality of vent openings. Ventilators usingthis configuration are most typically used for less acute clinicalrequirements, such as the treatment of obstructive sleep apnea orrespiratory insufficiency. In non-vented circuits, the patient interfaceis usually not provided with vent openings. Non-vented circuits can havesingle limb or dual limb patient circuits, and an exhalation valve.Ventilators using non-vented patient circuits are most typically usedfor critical care applications.

Vented patient circuits are used only to carry gas flow from theventilator to the patient and patient mask, and require a patient maskwith vent openings. When utilizing vented circuits, the patient inspiresfresh gas from the patient circuit, and expires CO2-enriched gas, whichis purged from the system through the vent openings in the mask. Thisconstant purging of flow through vent openings in the mask when usingsingle-limb circuits provides several disadvantages: 1) it requires theventilator to provide significantly more flow than the patient requires,adding cost/complexity to the ventilator and requiring larger tubing; 2)the constant flow through the vent openings creates and conducts noise,which has proven to be a significant detriment to patients with sleepapnea that are trying to sleep while wearing the mask; 3) the additionalflow coming into proximity of the patient's nose and then exiting thesystem often causes dryness in the patient, which often drives the needfor adding humidification to the system; and 4) patient-expired CO2flows partially out of the vent holes in the mask and partially into thepatient circuit tubing, requiring a minimum flow through the tubing atall times in order to flush the CO2 and minimize the re-breathing ofexhaled CO2. To address the problem of undesirable flow ofpatient-expired CO2 back into the patient circuit tubing, currentlyknown CPAP systems typically have a minimum-required pressure of 4 cmH2Owhenever the patient is wearing the mask, which often producessignificant discomfort, claustrophobia and/or feeling of suffocation toearly CPAP users and leads to a high (approximately 50%) non-compliancerate with CPAP therapy.

When utilizing non-vented dual limb circuits, the patient inspires freshgas from one limb (the “inspiratory limb”) of the patient circuit andexpires CO2-enriched gas from the second limb (the “expiratory limb”) ofthe patient circuit. Both limbs of the dual limb patient circuit areconnected together in a “Y” proximal to the patient to allow a singleconical connection to the patient mask. When utilizing non-vented singlelimb circuits, an expiratory valve is placed along the circuit, usuallyproximal to the patient. During the inhalation phase, the exhalationvalve is closed to the ambient and the patient inspires fresh gas fromthe single limb of the patient circuit. During the exhalation phase, thepatient expires CO2-enriched gas from the exhalation valve that is opento ambient. The single limb and exhalation valve are usually connectedto each other and to the patient mask with conical connections.

In the patient circuits described above, the ventilator pressurizes thegas to be delivered to the patient inside the ventilator to the intendedpatient pressure, and then delivers that pressure to the patient throughthe patient circuit. Very small pressure drops develop through thepatient circuit, typically around 1 cmH2O, due to gas flow though thesmall amount of resistance created by the tubing. Some ventilatorscompensate for this small pressure drop either by mathematicalalgorithms, or by sensing the tubing pressure more proximal to thepatient.

Ventilators that utilize a dual limb patient circuit typically includean exhalation valve at the end of the expiratory limb proximal to theventilator, while ventilators that utilize a single limb, non-ventedpatient circuit typically include an exhalation valve at the end of thesingle limb proximal to the patient as indicated above. Exhalationvalves can have fixed or adjustable PEEP (positive expiratory endpressure), typically in single limb configurations, or can be controlledby the ventilator. The ventilator controls the exhalation valve, closesit during inspiration, and opens it during exhalation. Lesssophisticated ventilators have binary control of the exhalation valve,in that they can control it to be either open or closed. Moresophisticated ventilators are able to control the exhalation valve in ananalog fashion, allowing them to control the pressure within the patientcircuit by incrementally opening or closing the valve. Valves thatsupport this incremental control are referred to as active exhalationvalves. In existing ventilation systems, active exhalation valves aremost typically implemented physically within the ventilator, and theremaining few ventilation systems with active exhalation valves locatethe active exhalation valve within the patient circuit proximal to thepatient. Active exhalation valves inside ventilators are typicallyactuated via an electromagnetic coil in the valve, whereas activeexhalation valves in the patient circuit are typically pneumaticallypiloted from the ventilator through a separate pressure source such asecondary blower, or through a proportional valve modulating thepressure delivered by the main pressure source.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a mask(e.g., a nasal pillows mask) for achieving positive pressure mechanicalventilation (inclusive of CPAP, ventilatory support, critical careventilation, emergency applications), and a method for a operating aventilation system including such mask. The mask preferably includes apressure sensing modality proximal to the patient connection. Suchpressure sensing modality may be a pneumatic port with tubing thatallows transmission of the patient pressure back to the ventilator formeasurement, or may include a transducer within the mask. The pressuresensing port is used in the system to allow pressure sensing forachieving and/or monitoring the therapeutic pressures. Alternately oradditionally, the mask may include a flow sensing modality locatedtherewithin for achieving and/or monitoring the therapeutic flows.

The mask of the present invention also includes a piloted exhalationvalve that is used to achieve the target pressures/flows to the patient.In the preferred embodiment, the pilot for the valve is pneumatic anddriven from the gas supply tubing from the ventilator. The pilot canalso be a preset pressure derived in the mask, a separate pneumatic linefrom the ventilator, or an electro-mechanical control. In accordancewith the present invention, the valve is preferably implemented with adiaphragm.

One of the primary benefits attendant to including the valve inside themask is that it provides a path for patient-expired CO2 to exit thesystem without the need for a dual-limb patient circuit, and without thedisadvantages associated with a single-limb patient circuit, such ashigh functional dead space. For instance, in applications treatingpatients with sleep apnea, having the valve inside the mask allowspatients to wear the mask while the treatment pressure is turned offwithout risk of re-breathing excessive CO2.

Another benefit for having the valve inside the mask is that it allowsfor a significant reduction in the required flow generated by theventilator for ventilating the patient since a continuous vented flowfor CO2 washout is not required. Lower flow in turn allows for thetubing size to be significantly smaller (e.g., 2-9 mm ID) compared toconventional ventilators (22 mm ID for adults; 8 mm ID for pediatric).However, this configuration requires higher pressures than the patient'stherapeutic pressure to be delivered by the ventilator. In this regard,pressure from the ventilator is significantly higher than the patient'stherapeutic pressure, though the total pneumatic power delivered isstill smaller than that delivered by a low pressure, high flowventilator used in conjunction with a vented patient circuit andinterface. One obvious benefit of smaller tubing is that it providesless bulk for patient and/or caregivers to manage. For today's smallestventilators, the bulk of the tubing is as significant as the bulk of theventilator. Another benefit of the smaller tubing is that is allows formore convenient ways of affixing the mask to the patient. For instance,the tubing can go around the patient's ears to hold the mask to theface, instead of requiring straps (typically called “headgear”) to affixthe mask to the face. Along these lines, the discomfort, complication,and non-discrete look of the headgear is another significant factorleading to the high non-compliance rate for CPAP therapy. Anotherbenefit to the smaller tubing is that the mask can become smallerbecause it does not need to interface with the large tubing. Indeed,large masks are another significant factor leading to the highnon-compliance rate for CPAP therapy since, in addition to beingnon-discrete, they often cause claustrophobia. Yet another benefit isthat smaller tubing more conveniently routed substantially reduces whatis typically referred to as “tube drag” which is the force that the tubeapplies to the mask, displacing it from the patient's face. This forcehas to be counterbalanced by headgear tension, and the mask movementsmust be mitigated with cushion designs that have great compliance. Thereduction in tube drag in accordance with the present invention allowsfor minimal headgear design (virtually none), reduced headgear tensionfor better patient comfort, and reduced cushion compliance that resultsin a smaller, more discrete cushion.

The mask of the present invention may further include a heat andmoisture exchanger (HME) which is integrated therein. The HME can fullyor at least partially replace a humidifier (cold or heated pass-over;active or passive) which may otherwise be included in the ventilationsystem employing the use of the mask. The HME is positioned within themask so as to be able to intercept the flow delivered from a flowgenerator to the patient in order to humidify it, and further tointercept the exhaled flow of the patient in order to capture humidityand heat for the next breath. The HME can also be used as a structuralmember of the mask, adding q cushioning effect and simplifying thedesign of the cushion thereof.

The present invention is best understood by reference to the followingdetailed description when read in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

These, as well as other features of the present invention, will becomemore apparent upon reference to the drawings wherein:

FIG. 1 is top perspective view of a nasal pillows mask constructed inaccordance with the present invention and including an integrateddiaphragm-based piloted exhalation valve;

FIG. 2 is an exploded view of the nasal pillows mask shown in FIG. 1;

FIG. 3 is a partial cross-sectional view of the nasal pillows mask shownin FIG. 1 taken along lines 3-3 thereof, and depicting the valve pilotlumen extending through the cushion of the mask;

FIG. 4 is a partial cross-sectional view of the nasal pillows mask shownin FIG. 1 taken along lines 4-4 thereof, and depicting the pressuresensing lumen extending through the cushion of the mask;

FIG. 5 is a cross-sectional view of the nasal pillows mask shown in FIG.1 taken along lines 5-5 thereof;

FIG. 6 is a top perspective view of cushion of the nasal pillows maskshown in FIG. 1;

FIG. 7 is a top perspective view of exhalation valve of the nasalpillows mask shown in FIG. 1;

FIG. 8 is a bottom perspective view of exhalation valve shown in FIG. 7;

FIG. 9 is a cross-sectional view of exhalation valve shown in FIGS. 7and 8;

FIG. 10 is a cross-sectional view similar to FIG. 5, but depicting avariant of the nasal pillows mask wherein an HME is integrated into thecushion thereof;

FIGS. 11A, 11B and 11C are a series of graphs which provide visualrepresentations corresponding to exemplary performance characteristicsof the exhalation valve subassembly of the nasal pillows mask of thepresent invention;

FIG. 12 is a schematic representation of an exemplary ventilation systemwherein a tri-lumen tube is used to facilitate the operative interfacebetween the nasal pillows mask and a flow generating device;

FIG. 13 is a schematic representation of an exemplary ventilation systemwherein a bi-lumen tube is used to facilitate the operative interfacebetween the nasal pillows mask and a flow generating device; and

FIG. 14 is a side-elevational view of the nasal pillows mask of thepresent invention depicting an exemplary manner of facilitating thecooperative engagement thereof to a patient through the use of aheadgear assembly.

Common reference numerals are used throughout the drawings and detaileddescription to indicate like elements.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein the showings are for purposes ofillustrating various embodiments of the present invention only, and notfor purposes of limiting the same, FIGS. 1-4 depict a ventilation mask10 (e.g., a nasal pillows mask) constructed in accordance with thepresent invention. Though the mask 10 is depicted as a nasal pillowsmask, those skilled in the art will recognize that other ventilationmasks are contemplated herein, such as nasal prongs masks, nasal masks,full face masks and oronasal masks. As such, for purposes of thisapplication, the term mask and/or ventilation mask is intended toencompass all such mask structures. The mask 10 includes an integrated,diaphragm-implemented, piloted exhalation valve 12, the structural andfunctional attributes of which will be described in more detail below.

As shown in FIGS. 1-5, the mask 10 comprises a housing or cushion 14.The cushion 14, which is preferably fabricated from a silicone elastomerhaving a Shore A hardness in the range of from about 20 to 60 andpreferably about 40, is formed as a single, unitary component, and isshown individually in FIG. 6. The cushion 14 includes a main bodyportion 16 which defines a first outer end surface 18 and an opposedsecond outer end surface 20. The main body portion 16 further defines aninterior fluid chamber 22 which is of a prescribed volume. In additionto the main body portion 16, the cushion 14 includes an identicallyconfigured pair of hollow pillow portions 24 which protrude from themain body portion 16 in a common direction and in a prescribed spatialrelationship relative to each other. More particularly, in the cushion14, the spacing between the pillow portions 24 is selected to facilitatethe general alignment thereof with the nostrils of an adult patient whenthe mask 10 is worn by such patient. As seen in FIGS. 3 and 4, each ofthe pillow portions 24 fluidly communicates with the fluid chamber 22.

As shown in FIG. 2, the main body portion 16 of the cushion 14 includesan enlarged, circularly configured valve opening 26 which is in directfluid communication with the fluid chamber 22. The valve opening 26 ispositioned in generally opposed relation to the pillow portions 24 ofthe cushion 14, and is circumscribed by an annular valve seat 27 alsodefined by the main body portion 16. As also shown in FIG. 2, the mainbody portion 16 further defines opposed first and second inner endsurfaces 28, 30 which protrude outwardly from the periphery of the valveopening 26, and are diametrically opposed relative thereto so as to bespaced by an interval of approximately 180°. The valve opening 26, valveseat 27, and first and second inner end surfaces 28, 30 are adapted toaccommodate the exhalation valve 12 of the mask 10 in a manner whichwill be described in more detail below.

As shown FIGS. 3-6, the main body portion 16 of the cushion 14 furtherdefines first and second gas delivery lumens 32, 34 which extend fromrespective ones of the first and second outer end surfaces 18, 20 intofluid communication with the fluid chamber 22. Additionally, a pressuresensing lumen 36 defined by the main body portion extends from the firstouter end surface 18 into fluid communication with the fluid chamber 22.The main body portion 16 further defines a valve pilot lumen 38 whichextends between the second outer end surface 20 and the second inner endsurface 30. The use of the first and second gas delivery lumens 32, 34,the pressure sensing lumen 36, and the valve pilot lumen 38 will also bediscussed in more detail below. Those of ordinary skill in the art willrecognize that the gas delivery lumens 32, 34, may be substituted with asingle gas delivery lumen and/or positioned within the cushion 14 inorientations other than those depicted in FIG. 6. For example, the gasdelivery lumen(s) of the cushion 14 may be positioned frontally,pointing upwardly, pointing downwardly, etc. rather than extendinglaterally as shown in FIG. 6.

Referring now to FIGS. 2-5 and 7-9, the exhalation valve 12 of the mask10 is made of three (3) parts or components, and more particularly aseat member 40, a cap member 42, and a diaphragm 44 which is operativelycaptured between the seat and cap members 40, 42. The seat and capmembers 40, 42 are each preferably fabricated from a plastic material,with the diaphragm 44 preferably being fabricated from an elastomerhaving a Shore A hardness in the range of from about 20-40.

As is most easily seen in FIGS. 2, 7 and 9, the seat member 40 includesa tubular, generally cylindrical wall portion 46 which defines a distal,annular outer rim 48 and an opposed annular inner seating surface 49. Asshown in FIG. 9, the diameter of the outer rim 48 exceeds that of theseating surface 49. Along these lines, the inner surface of the wallportion 46 is not of a uniform inner diameter, but rather is segregatedinto first and second inner surface sections which are of differinginner diameters, and separated by an annular shoulder 51. In addition tothe wall portion 46, the seat member 40 includes an annular flangeportion 50 which protrudes radially from that end of the wall portion 46opposite the outer rim 48. As shown in FIGS. 2 and 7, the flange portion50 includes a plurality of exhaust vents 52 which are located about theperiphery thereof in a prescribed arrangement and spacing relative toeach other. Additionally, as is apparent from FIG. 9, the seat member 40is formed such that each of the exhaust vents 52 normally fluidlycommunicates with the bore or fluid conduit defined by the wall portion46.

The cap member 42 of the exhaust valve 12 comprises a circularlyconfigured base portion 54 which defines an inner surface 56 and anopposed outer surface 58. In addition to the base portion 54, the capmember 42 includes an annular flange portion 60 which circumvents andprotrudes generally perpendicularly relative to the inner surface 56 ofthe base portion 60. The flange portion 60 defines a distal annularshoulder 62. As shown in FIG. 9, the shoulder 62 and inner surface 56extend along respective ones of a spaced, generally parallel pair ofplanes. Further, as shown in FIG. 8, formed in the outer surface 58 ofthe base portion 54 is an elongate groove 64 which extends diametricallyacross the outer surface 58. The use of the groove 64 will be describedin more detail below. The seat and cap members 40, 42, when attached toeach other in the fully assembled exhalation valve 12, collectivelydefine an interior valve chamber 59 of the exhalation valve 12. Moreparticularly, such valve chamber 59 is generally located between theinner surface 56 defined by the base portion 54 of the cap member 42 andthe seating surface 49 defined by the wall portion 46 of the seat member40.

The diaphragm 44 of the exhalation valve 12, which resides within thevalve chamber 59, has a circularly configured, central body portion 66,and a peripheral flange portion 68 which is integrally connected to andcircumvents the body portion 66. The body portion 66 includes an annularlip 72 which circumvents and protrudes upwardly from one side or facethereof. The flange portion 68 includes an arcuately contoured primaryregion and a distal region which protrudes radially from the primaryregion. As such, the primary region of the flange portion 68 extendsbetween the distal region thereof and the body portion 66, and defines acontinuous, generally concave channel 70.

In the exhalation valve 12, the flange portion 68 of the diaphragm 44 isoperatively captured between the flange portions 50, 60 of the seat andcap members 40, 42. More particularly, the annular distal region of theflange portion 68 is compressed (and thus captured) between the shoulder62 defined by the flange portion 60 of the cap member 42, and acomplimentary annular shoulder 53 which is defined by the flange portion50 of the seat member 40 proximate the exhaust vents 52. The orientationof the diaphragm 44 within the valve chamber 59 when captured betweenthe seat and cap members 40, 42 is such that the channel 70 defined bythe arcuately contoured primary region of the flange portion 68 isdirected toward or faces the seating surface 49 defined by the wallportion 46 of the seat member 40.

The diaphragm 44 (and hence the exhalation valve 12) is selectivelymoveable between an open position (shown in FIGS. 3-5 and 9) and aclosed position. When in its normal, open position, the diaphragm 44 isin a relaxed, unbiased state. Importantly, in either of its open orclosed positions, the diaphragm 44 is not normally seated directlyagainst the inner surface 56 defined by the base portion 54 of the capmember 42. Rather, a gap is normally maintained between the body portion66 of the diaphragm 44 and the inner surface 56 of the base portion 54.The width of such gap when the diaphragm 44 is in its open position isgenerally equal to the fixed distance separating the inner surface 56 ofthe base portion 54 from the shoulder 62 of the flange portion 60.Further, when the diaphragm 44 is in its open position, the body portion66, and in particular the lip 72 protruding therefrom, is itselfdisposed in spaced relation to the seating surface 49 defined by thewall portion 46 of the seat member 40. As such, when the diaphragm 44 isin its open position, fluid is able to freely pass through the fluidconduit defined by the wall portion 46, between the seating surface 49and diaphragm 44, and through the exhaust vents 52 to ambient air. Asshown in FIGS. 3, 8 and 9, the flange portion 60 of the cap member 42 isfurther provided with a pilot port 74 which extends therethrough and, inthe fully assembled exhalation valve 12, fluidly communicates with thatportion of the valve chamber 59 disposed between the body portion 66 ofthe diaphragm 44 and the inner surface 56 of the base portion 54. Theuse of the pilot port 74 will also be described in more detail below.

As will be discussed in more detail below, in the exhalation valve 12,the diaphragm 44 is resiliently deformable from its open position (towhich it may be normally biased) to its closed position. An importantfeature of the present invention is that the diaphragm 44 is normallybiased to its open position which provides a failsafe to allow a patientto inhale ambient air through the exhalation valve 12 and exhale ambientair therethrough (via the exhaust vents 52) during any ventilatormalfunction or when the mask is worn without the therapy being deliveredby the ventilator. When the diaphragm 44 is moved or actuated to itsclosed position, the lip 72 of the body portion 66 is firmly seatedagainst the seating surface 49 defined by the wall portion 46 of theseat member 40. The seating of the lip 72 against the seating surface 49effectively blocks fluid communication between the fluid conduit definedby the wall portion 46 and the valve chamber 59 (and hence the exhaustvents 52 which fluidly communicate with the valve chamber 59).

In the mask 10, the cooperative engagement between the exhalation valve12 and the cushion 14 is facilitated by the advancement of the wallportion 46 of the seat member 40 into the valve opening 26 defined bythe cushion 14. As best seen in FIG. 5, such advancement is limited bythe ultimate abutment or engagement of a beveled seating surface 76defined by the flange portion 50 of the seat member 40 against thecomplimentary valve seat 27 of the cushion 14 circumventing the valveopening 26. Upon the engagement of the seating surface 76 to the valveseat 27, the fluid chamber 22 of the cushion 14 fluidly communicateswith the fluid conduit defined by the wall portion 46 of the seat member40. As will be recognized, if the diaphragm 44 resides in its normal,open position, the fluid chamber 22 is further placed into fluidcommunication with the valve chamber 59 via the fluid conduit defined bythe wall portion 46, neither end of which is blocked or obstructed byvirtue of the gap defined between the lip 72 of the diaphragm 44 and theseating surface 49 of the wall portion 46.

When the exhalation valve 12 is operatively coupled to the cushion 14,in addition to the valve seat 27 being seated against the seatingsurface 76, the first and second inner end surfaces 28, 30 of thecushion 14 are seated against respective, diametrically opposed sectionsof the flange portion 68 defined by the cap member 42. As best seen inFIGS. 3 and 4, the orientation of the exhalation valve 12 relative tothe cushion 14 is such that the end of the valve pilot lumen 38extending to the second inner end surface 30 is aligned and fluidlycommunicates with the pilot port 74 within the flange portion 60. Assuch, in the mask 10, the valve pilot lumen 38 is in continuous, fluidcommunication with that portion of the valve chamber 59 defined betweenthe inner surface 56 of the base portion 54 and the body portion 66 ofthe diaphragm 44.

To assist in maintaining the cooperative engagement between theexhalation valve 12 and the cushion 14, the mask 10 is furtherpreferably provided with an elongate frame member 78. The frame member78 has a generally V-shaped configuration, with a central portionthereof being accommodated by and secured within the complimentarygroove 64 formed in the outer surface 58 defined by the base portion 54of the cap member 42. As shown in FIGS. 3 and 4, the opposed endportions of the frame members 78 are cooperatively engaged to respectiveones of the first and second outer end surfaces 18, 20 of the cushion14. More particularly, as shown in FIG. 2, the frame member 78 includesan identically configured pair of first and second connectors 80, 82which extend from respective ones of the opposed end portions thereof.An inner portion of the first connector 80 is advanced into andfrictionally retained within the first gas delivery lumen 32 of thecushion 14. Similarly, an inner portion of the second connector 82 isadvanced into and frictionally retained within the second gas deliverylumen 34 of the cushion 14. In addition to the inner portions advancedinto respective ones of the first and second gas delivery lumens 32, 34,the first and second connectors 80, 82 of the frame member 78 eachfurther include an outer portion which, as will be described in moredetail below, is adapted to be advanced into and frictionally retainedwithin a corresponding lumen of a respective one of a pair of bi-lumentubes fluidly coupled to the mask 10.

As shown in FIGS. 3 and 4, the frame member 78 further includes atubular, cylindrically configured pressure port 84 which is disposedadjacent the first connector 80. The pressure port 84 is aligned andfluidly communicates with the pressure sensing lumen 36 of the cushion14. Similarly, the frame member 78 is also provided with a tubular,cylindrically configured pilot port 86 which is disposed adjacent thesecond connector 82. The pilot port 86 is aligned and fluidlycommunicates with the valve pilot lumen 38 of the cushion 14. As willalso be discussed in more detail below, the pressure and pilot ports 84,86 of the frame member 78 are adapted to be advanced into andfrictionally maintained within corresponding lumens of respective onesof the aforementioned pair of bi-lumen tubes which are fluidly connectedto the mask 10 within a ventilation system incorporating the same. Thereceipt of the frame member 78 within the groove 64 of the cap member 42ensures that the cushion 14, the exhalation valve 12 and the framemember 78 are properly aligned, and prevents relative movementtherebetween. Though not shown, it is contemplated that in one potentialvariation of the mask 10, the cushion 14 may be formed so as not toinclude the valve pilot lumen 38. Rather, a suitable valve pilot lumenwould be formed directly within the frame member 78 so as to extendtherein between the pilot port 86 thereof and the pilot port 74 of theexhalation valve 12.

In the mask 10, the exhalation valve 12 is piloted, with the movement ofthe diaphragm 44 to the closed position described above beingfacilitated by the introduction of positive fluid pressure into thevalve chamber 59. More particularly, it is contemplated that during theinspiratory phase of the breathing cycle of a patient wearing the mask10, the valve pilot lumen 38 will be pressurized by a pilot line fluidlycoupled to the pilot port 86, with pilot pressure being introduced intothat portion of the valve chamber 59 normally defined between the bodyportion 66 of the diaphragm 44 and the inner surface 56 defined by thebase portion 54 of the cap member 42 via the pilot port 74 extendingthrough the flange portion 60 of the cap member 42. The fluid pressurelevel introduced into the aforementioned region of the valve chamber 59via the pilot port 74 will be sufficient to facilitate the movement ofthe diaphragm 44 to its closed position described above.

Conversely, during the expiratory phase of the breathing cycle of thepatient wearing the mask 10, it is contemplated that the discontinuationor modulation of the fluid pressure through the valve pilot lumen 38 andhence into the aforementioned region of the valve chamber 59 via thepilot port 74, coupled with the resiliency of the diaphragm 44 and/orpositive pressure applied to the body portion 66 thereof, willfacilitate the movement of the diaphragm 44 back to the open position orto a partially open position. In this regard, positive pressure as maybe used to facilitate the movement of the diaphragm 44 to its openposition may be provided by air which is exhaled from the patient duringthe expiratory phase of the breathing circuit and is applied to the bodyportion 66 via the pillows portions 24 of the cushion 14, the fluidchamber 22, and the fluid conduit defined by the wall portion of theseat member 40. As will be recognized, the movement of the diaphragm 44to the open position allows the air exhaled from the patient to bevented to ambient air after entering the valve chamber 59 via theexhaust vents 52 within the flange portion 50 of the seat member 40which, as indicated above, fluidly communicate with the valve chamber59.

As will be recognized, based on the application of pilot pressurethereto, the diaphragm 44 travels from a fully open position through apartially open position to a fully closed position. In this regard, thediaphragm 44 will be partially open or partially closed duringexhalation to maintain desired ventilation therapy. Further, when pilotpressure is discontinued to the diaphragm 44, it moves to an openposition wherein the patient can inhale and exhale through the mask 10with minimal restriction and with minimal carbon dioxide retentiontherein. This is an important feature of the present invention whichallows a patient to wear the mask 10 without ventilation therapy beingapplied to the mask 10, the aforementioned structural and functionalfeatures of the mask 10 making it more comfortable to wear, and furtherallowing it to be worn without carbon dioxide buildup. This feature ishighly advantageous for the treatment of obstructive sleep apnea whereinpatients complain of discomfort with ventilation therapy due to mask andpressure discomfort. When it is detected that a patient requires sleepapnea therapy, the ventilation therapy can be started (i.e., in anobstructive sleep apnea situation).

To succinctly summarize the foregoing description of the structural andfunctional features of the mask 10, during patient inhalation, the valvepilot lumen 38 is pressurized, which causes the diaphragm 44 to closeagainst the seating surface 49, thus effectively isolating the fluidchamber 22 of the mask 10 from the outside ambient air. The entire flowdelivered from a flow generator fluidly coupled to the mask 10 isinhaled by the patient, assuming that unintentional leaks at theinterface between the cushion 14 and the patient are discarded. Thisfunctionality differs from what typically occurs in a conventional CPAPmask, where venting to ambient air is constantly open, and anintentional leak flow is continuously expelled to ambient air. Duringpatient exhalation, the pilot pressure introduced into the valve pilotlumen 38 is controlled so that the exhaled flow from the patient can beexhausted to ambient air through the exhalation valve 12 in theaforementioned manner. In this regard, the pilot pressure is “servoed”so that the position of the diaphragm 44 relative to the seating surface49 is modulated, hence modulating the resistance of the exhalation valve12 to the exhaled flow and effectively ensuring that the pressure in thefluid chamber 22 of the mask 10 is maintained at a prescribedtherapeutic level throughout the entire length of the exhalation phase.When the valve pilot lumen 38 is not pressurized, the exhalation valve12 is in a normally open state, with the diaphragm 44 being spaced fromthe seating surface 49 in the aforementioned manner, thus allowing thepatient to spontaneously breathe in and out with minimal pressure drop(also referred to as back-pressure) in the order of less than about 2 cmH2O at 60 l/min. As a result, the patient can comfortably breathe whilewearing the mask 10 and while therapy is not being administered to thepatient.

Referring now to FIGS. 11A, 11B and 11C, during use of the mask 10 by apatient, the functionality of the exhalation valve 12 can becharacterized with three parameters. These are Pt which is the treatmentpressure (i.e., the pressure in the mask 10 used to treat the patient;Pp which is the pilot pressure (i.e., the pressure used to pilot thediaphragm 44 in the exhalation valve 12); and Qv which is vented flow(i.e., flow that is exhausted from inside the exhalation valve 12 toambient. These three particular parameters are labeled as Pt, Pp and Qvin FIG. 9. When the patient is ventilated, Pt is greater than zero, withthe functionality of the exhalation valve 12 being described by thefamily of curves in the first and second quadrants of FIG. 11A. In thisregard, as apparent from FIG. 11A, for any given Pt, it is evident thatby increasing the pilot pressure Pp, the exhalation valve 12 will closeand the vented flow will decrease. A decrease in the pilot pressure Ppwill facilitate the opening of the valve 12, thereby increasing ventedflow. The vented flow will increase until the diaphragm 44 touches orcontacts the inner surface 56 of the base portion 54 of the cap member42, and is thus not able to open further. Conversely, when the patientis not ventilated, the inspiratory phase can be described by the thirdand fourth quadrants. More particularly, Qv is negative and air entersthe mask 10 through the valve 12, with the pressure Pt in the mask 10being less than or equal to zero. Pilot pressure Pp less than zero isnot a configuration normally used during ventilation of the patient, butis depicted for a complete description of the functionality of the valve12. The family of curves shown in FIG. 11A can be described by aparametric equation. Further, the slope and asymptotes of the curvesshown in FIG. 11A can be modified by, for example and not by way oflimitation, changing the material used to fabricate the diaphragm 44,changing the thickness of the diaphragm 44, changing the area ratiobetween the pilot side and patient side of the diaphragm 44, changingthe clearance between the diaphragm 44 and the seating surface 49,and/or changing the geometry of the exhaust vents 52.

An alternative representation of the functional characteristics of thevalve 12 can be described by graphs in which ΔP=Pt−Pp is shown. Forexample, the graph of FIG. 11B shows that for any given Pt, the ventedflow can be modulated by changing ΔP. In this regard, ΔP can beinterpreted as the physical position of the diaphragm 44. Since thediaphragm 44 acts like a spring, the equation describing the relativeposition d of the diaphragm 44 from the seating surface 49 of the seatmember 40 is k·d+Pt·At=Pp·Ap, where At is the area of the diaphragm 44exposed to treatment pressure Pt and Ap is the area of the diaphragm 44exposed to the pilot pressure Pp. A similar, alternative representationis provided in the graph of FIG. 11C which shows Pt on the x-axis and ΔPas the parameter. In this regard, for any given ΔP, the position d ofthe diaphragm 44 is determined, with the valve 12 thus being consideredas a fixed opening valve. In this scenario Pt can be considered thedriving pressure pushing air out of the valve 12, with FIG. 11C furtherillustrating the highly non-linear behavior of the valve 12.

FIG. 12 provides a schematic representation of an exemplary ventilationsystem 88 wherein a tri-lumen tube 90 is used to facilitate the fluidcommunication between the mask 10 and a blower or flow generator 92 ofthe system 88. As represented in FIG. 12, one end of the tri-lumen tube90 is fluidly connected to the flow generator 92, with the opposite endthereof being fluidly connected to a Y-connector 94. The three lumensdefined by the tri-lumen tube 90 include a gas delivery lumen, apressure sensing lumen, and a valve pilot lumen. The gas delivery lumenis provided with an inner diameter or ID in the range of from about 2 mmto 15 mm, and preferably about 4 mm to 10 mm. The pressure sensing andvalve pilot lumens of the tri-lumen tube 90 are each preferably providedwith an ID in the range of from about 0.5 mm to 2 mm. The outer diameteror OD of the tri-lumen tube 90 is preferably less than 17 mm, with thelength thereof in the system 88 being about 2 m. The Y-connector 94effectively bifurcates the tri-lumen tube 90 into the first and secondbi-lumen tubes 96, 98, each of which has a length of about 6 inches. Thefirst bi-lumen tube 96 includes a gas delivery lumen having an ID in thesame ranges described above in relation to the gas delivery lumen of thetri-lumen tube 90. The gas delivery lumen of the first bi-lumen tube 96is fluidly coupled to the outer portion of the first connector 80 of theframe member 78. The remaining lumen of the first bi-lumen tube 96 is apressure sensing lumen which has an ID in the same range described abovein relation to the pressure sensing lumen of the tri-lumen tube 90, andis fluidly coupled to the pressure port 84 of the frame member 78.Similarly, the second bi-lumen tube 98 includes a gas delivery lumenhaving an ID in the same ranges described above in relation to the gasdelivery lumen of the tri-lumen tube 90. The gas delivery lumen of thesecond bi-lumen tube 98 is fluidly coupled to the outer portion of thesecond connector 82 of the frame member 78. The remaining lumen of thesecond bi-lumen tube 98 is a valve pilot lumen which has an ID in thesame range described above in relation to the valve pilot lumen of thetri-lumen tube 90, and is fluidly coupled to the pilot port 86 of theframe member 78.

In the system 88 shown in FIG. 12, the pilot pressure is generated atthe flow generator 92. In the prior art, a secondary blower orproportional valve that modulates the pressure from a main blower isused to generate a pressure to drive an expiratory valve. However, inthe system 88 shown in FIG. 12, the outlet pressure of the flowgenerator 92 is used, with the flow generator 92 further beingcontrolled during patient exhalation in order to have the correct pilotpressure for the exhalation valve 12. This allows the system 88 to beinexpensive, not needing additional expensive components such asproportional valves or secondary blowers.

FIG. 13 provides a schematic representation of another exemplaryventilation system 100 wherein a bi-lumen tube 102 is used to facilitatethe fluid communication between the mask 10 and the blower or flowgenerator 92 of the system 100. As represented in FIG. 13, one end ofthe bi-lumen tube 102 is fluidly connected to the flow generator 92,with the opposite end thereof being fluidly connected to the Y-connector94. The two lumens defined by the bi-lumen tube 102 include a gasdelivery lumen and a pressure sensing lumen. The gas delivery lumen isprovided with an inner diameter or ID in the range of from about 2 mm to10 mm, and preferably about 4 mm to 7 mm. The pressure sensing lumen ofthe bi-lumen tube 102 is preferably provided with an ID in the range offrom about 0.5 mm to 2 mm. The outer diameter or OD of the bi-lumen tube90 is preferably less than 11 mm, with the length thereof being about 2m. The Y-connector 94 effectively bifurcates the bi-lumen tube 102 intothe first and second bi-lumen tubes 96, 98, each of which has a lengthof about 6 inches. The first bi-lumen tube 96 includes a gas deliverylumen having an ID in the same ranges described above in relation to thegas delivery lumen of the bi-lumen tube 102. The gas delivery lumen ofthe first bi-lumen tube 96 is fluidly coupled to the outer portion ofthe first connector 80 of the frame member 78. The remaining lumen ofthe first bi-lumen tube 96 is a pressure sensing lumen which has an IDin the same range described above in relation to the pressure sensinglumen of the bi-lumen tube 102, and is fluidly coupled to the pressureport 84 of the frame member 78. Similarly, the second bi-lumen tube 98includes a gas delivery lumen having an ID in the same ranges describedabove in relation to the gas delivery lumen of the bi-lumen tube 102.The gas delivery lumen of the second bi-lumen tube 98 is fluidly coupledto the outer portion of the second connector 82 of the frame member 78.The remaining lumen of the second bi-lumen tube 98 is a valve pilotlumen which has an ID in the same range described above in relation tothe pressure sensing lumen of the bi-lumen tube 102, and is fluidlycoupled to the pilot port 86 of the frame member 78.

In the system 100 shown in FIG. 13, the valve pilot lumen 38 isconnected to the gas delivery air path at the Y-connector 94. Moreparticularly, the gas delivery lumen of the bi-lumen tube 102 istransitioned at the Y-connector 94 to the valve pilot lumen of thesecond bi-lumen tube 98. As such, the pilot pressure will beproportional to the outlet pressure of the flow generator 92 minus thepressure drop along the bi-lumen tube 102, which is proportional todelivered flow. This solution is useful when small diameter tubes areused in the system 100, since such small diameter tubes require higheroutlet pressure from the flow generator 92 for the same flow. In thisregard, since the pressure at the outlet of the flow generator 92 wouldbe excessive for piloting the exhalation valve 12, a lower pressurealong the circuit within the system 100 is used. In the system 100,though it is easier to tap in at the Y-connector 94, anywhere along thetube network is acceptable, depending on the pressure level of the flowgenerator 92 which is the pressure required by the patient circuit inorder to deliver the therapeutic pressure and flow at the patient.

In each of the systems 88, 100, it is contemplated that the control ofthe flow generator 92, and hence the control of therapeutic pressuredelivered to the patient wearing the mask 10, may be governed by thedata gathered from dual pressure sensors which take measurements at themask 10 and the output of the flow generator 92. As will be recognized,pressure sensing at the mask 10 is facilitated by the pressure sensinglumen 36 which, as indicated above, is formed within the cushion 14 andfluidly communicates with the fluid chamber 22 thereof. As alsopreviously explained, one of the lumens of the first bi-lumen tube 96 ineach of the systems 88, 100 is coupled to the pressure port 84 (andhence the pressure sensing lumen 36). As a result, the first bi-lumentube 96, Y-connector 94 and one of the tri-lumen or bi-lumen tubes 90,102 collectively define a continuous pressure sensing fluid path betweenthe mask 10 and a suitable pressure sensing modality located remotelytherefrom. A more detailed discussion regarding the use of the dualpressure sensors to govern the delivery of therapeutic pressure to thepatient is found in Applicant's co-pending U.S. application Ser. No.13/411,257 entitled Dual Pressure Sensor Continuous Positive AirwayPressure (CPAP) Therapy filed Mar. 2, 2012, the entire disclosure ofwhich is incorporated herein by reference.

Referring now to FIG. 10, there is shown a mask 10 a which comprises avariant of the mask 10. The sole distinction between the masks 10, 10 alies in the mask 10 a including a heat and moisture exchanger or HME 104which is positioned within the fluid chamber 22 of the cushion 14. TheHME 104 is operative to partially or completely replace a humidifier(cold or heated pass-over; active or passive) which would otherwise befluidly coupled to the mask 10 a. This is possible because the averageflow through the system envisioned to be used in conjunction with themask 10 a is about half of a prior art CPAP mask, due to the absence ofany intentional leak in such system.

The HME 104 as a result of its positioning within the fluid chamber 22,is able to intercept the flow delivered from the flow generator to thepatient in order to humidify it, and is further able to capture humidityand heat from exhaled flow for the next breath. The pressure dropcreated by the HME 104 during exhalation (back-pressure) must belimited, in the order of less than 5 cmH2O at 60 l/min, and preferablylower than 2 cmH2O at 60 l/min. These parameters allow for a lowback-pressure when the patient is wearing the mask 10 a and no therapyis delivered to the patient.

It is contemplated that the HME 104 can be permanently assembled to thecushion 14, or may alternatively be removable therefrom and thuswashable and/or disposable. In this regard, the HME 104, if removablefrom within the cushion 14, could be replaced on a prescribedreplacement cycle. Additionally, it is contemplated that the HME 104 canbe used as an elastic member that adds elasticity to the cushion 14. Inthis regard, part of the elasticity of the cushion 14 may beattributable to its silicone construction, and further be partlyattributable to the compression and deflection of the HME 104 inside thecushion 14.

The integration of the exhalation valve 12 into the cushion 14 and inaccordance with the present invention allows lower average flow comparedto prior art CPAP masks. As indicated above, normal masks have a set ofapertures called “vents” that create a continuous intentional leakduring therapy. This intentional leak or vented flow is used to flushout the exhaled carbon dioxide that in conventional CPAP machines, witha standard ISO taper tube connecting the mask to the flow generator orblower, fills the tubing up almost completely with carbon dioxide duringexhalation. The carbon dioxide accumulated in the tubing, if not flushedout through the vent flow, would be inhaled by the patient in the nextbreath, progressively increasing the carbon dioxide content in theinhaled gas at every breath. The structural/functional features of theexhalation valve 12, in conjunction with the use of small innerdiameter, high pneumatic resistance tubes in the system in which themask 10, 10 a is used, ensures that all the exhaled gas goes to ambient.As a result, a vent flow is not needed for flushing any trapped carbondioxide out of the system. Further, during inspiration the exhalationvalve 12 can close, and the flow generator of the system needs todeliver only the patient flow, without the additional overhead of theintentional leak flow. In turn, the need for lower flow rates allows forthe use of smaller tubes that have higher pneumatic resistance, withoutthe need for the use of extremely powerful flow generators. Thepneumatic power through the system can be kept comparable to those oftraditional CPAP machines, though the pressure delivered by the flowgenerator will be higher and the flow lower.

The reduced average flow through the system in which the mask 10, 10 ais used means that less humidity will be removed from the system, aswell as the patient. Conventional CPAP systems have to reintegrate thehumidity vented by the intentional leak using a humidifier, with heatedhumidifiers being the industry standard. Active humidificationintroduces additional problems such as rain-out in the system tubing,which in turn requires heated tubes, and thus introducing morecomplexity and cost into the system. The envisioned system of thepresent invention, as not having any intentional leak flow, does notneed to introduce additional humidity into the system. As indicatedabove, the HME 104 can be introduced into the cushion 14 of the mask 10a so that exhaled humidity can be trapped and used to humidify the airfor the following breath.

In addition, a big portion of the noise of conventional CPAP systems isnoise conducted from the flow generator through the tubing up to themask and then radiated in the ambient through the vent openings. Aspreviously explained, the system described above is closed to theambient during inhalation which is the noisiest part of the therapy. Theexhaled flow is also lower than the prior art so it can be diffused moreefficiently, thus effectively decreasing the average exit speed andminimizing impingement noise of the exhaled flow on bed sheets, pillows,etc.

As also explained above, a patient can breathe spontaneously when themask is worn and not connected to the flow generator tubing, or whentherapy is not administered. In this regard, there will be little backpressure and virtually no carbon dioxide re-breathing, due to thepresence of the exhalation valve 12 that is normally open and the innerdiameters of the tubes integrated into the system. This enables a zeropressure start wherein the patient falls asleep wearing the mask 10, 10a wherein the flow generator does not deliver any therapy. Prior artsystems can only ramp from about 4mH2O up to therapy pressure. A zeropressure start is more comfortable to patients that do not toleratepressure.

As seen in FIG. 14, due to the reduced diameter of the various tubes(i.e., the tri-lumen tube 90 and bi-lumen tubes 96, 98, 102) integratedinto the system 88, 100, such tubes can be routed around the patient'sears similar to conventional O2 cannulas. More particularly, the tubingcan go around the patient's ears to hold the mask 10, 10 a to thepatient's face. This removes the “tube drag” problem described abovesince the tubes will not pull the mask 10, 10 a away from the face ofthe patient when he or she moves. As previously explained, “tube drag”typically decreases mask stability on the patient and increasesunintentional leak that annoys the patient. In the prior art, head geartension is used to counter balance the tube drag, which leads to comfortissues. The tube routing of the present invention allows for lower headgear tension and a more comfortable therapy, especially for compliantpatients that wear the mask 10 approximately eight hours every night.The reduction in tube drag in accordance with the present invention alsoallows for minimal headgear design (virtually none), reduced headgeartension for better patient comfort as indicated above, and reducedcushion compliance that results in a smaller, more discrete cushion 14.The tube dangling in front of the patient, also commonly referred to asthe “elephant trunk” by patients, is a substantial psychological barrierto getting used to therapy. The tube routing shown in FIG. 14, inaddition to making the mask 10, 10 a more stable upon the patient,avoids this barrier as well. Another benefit to the smaller tubing isthat the mask 10, 10 a can become smaller because it does not need tointerface with large tubing. Indeed, large masks are another significantfactor leading to the high non-compliance rate for CPAP therapy since,in addition to being non-discrete, they often cause claustrophobia.

This disclosure provides exemplary embodiments of the present invention.The scope of the present invention is not limited by these exemplaryembodiments. Numerous variations, whether explicitly provided for by thespecification or implied by the specification, such as variations instructure, dimension, type of material and manufacturing process may beimplemented by one of skill in the art in view of this disclosure.

What is claimed is:
 1. A ventilation mask, comprising: a housingdefining an interior chamber and a valve pilot lumen; and an exhalationvalve cooperatively engaged to the housing and fluidly coupled to thevalve pilot lumen; the exhalation valve being piloted in a manner whichfacilitates the selective movement thereof from an open position towhich it is normally biased and wherein at least a portion of theinterior chamber is vented to ambient air, to a closed position whereinfluid flow between the interior chamber and ambient air is at leastpartially obstructed thereby, the valve pilot lumen being adapted toselectively apply a pilot fluid pressure to the exhalation valve in amanner facilitating the movement thereof.
 2. The ventilation mask ofclaim 1 wherein the housing further defines at least one gas deliverylumen which fluidly communicates with the interior chamber.
 3. Theventilation mask of claim 2 wherein the housing further defines pressuresensing lumen which fluidly communicates with the interior chamber. 4.The ventilation mask of claim 1 wherein the ventilation mask is selectedfrom the group consisting of a nasal pillows mask, a nasal prongs mask,a nasal mask, a full face masks, a total face mask, and an oronasalmask.
 5. The ventilation mask of claim 1 wherein the housing is sizedand configured to be positionable between a patient's nose and mouth. 6.The ventilation mask of claim 5 wherein the housing is a resilientcushion including a spaced pair of hollow pillow portions which eachfluidly communicate with the interior chamber and are adapted to engagerespective ones of the nostrils of the patient's nose.
 7. Theventilation mask of claim 6 further comprising a heat and moistureexchanger disposed within the interior chamber between the exhalationvalve and the pillow portions of the cushion.
 8. The ventilation mask ofclaim 1 wherein the exhalation valve is configured to completelyobstruct fluid flow between the interior chamber and ambient air when inthe closed position.
 9. The ventilation mask of claim 1 wherein theexhalation valve is configured to vent the entirety of the interiorchamber to ambient air when in the open position.
 10. The ventilationmask of claim 1 wherein the exhalation valve is configured to adjustfluid flow between the interior chamber and ambient air when disposedbetween the closed position and the open position.
 11. The ventilationmask of claim 1 wherein the exhalation valve comprises a diaphragm whichis fabricated from a resilient material and movable between the closedand open positions.
 12. The ventilation mask of claim 11 wherein: theexhalation valve defines a valve chamber; and the diaphragm resideswithin the valve chamber and is sized and configured relative theretosuch that the valve chamber is maintained in constant fluidcommunication with ambient air and the valve pilot lumen, is placed intofluid communication with the interior chamber when the diaphragm is inthe open position, and is substantially fluidly isolated from theinterior chamber when the diaphragm is in the closed position.
 13. Theventilation mask of claim 12 wherein: the exhalation valve comprises aseat member and a cap member which are attached to each other andcollectively define the valve chamber thereof; the diaphragm is capturedbetween the seat and cap members in a manner wherein the diaphragmeffectively segregates the valve chamber into a first section whichfluidly communicates with the valve pilot lumen when the diaphragm is ineither of the open and closed positions, and a second section whichfluidly communicates with the interior chamber and ambient air when thediaphragm is in the open position.
 14. The ventilation mask of claim 13wherein the seat member further includes a plurality of vents which areformed therein and collectively define a flow conduit between theinterior chamber and ambient air when the diaphragm is in the openposition.
 15. The ventilation mask of claim 1 wherein the exhalationvalve at least partially resides within the interior chamber.
 16. Aventilation mask, comprising: a housing defining an interior chamber, avalve pilot lumen, and at least one gas delivery lumen which fluidlycommunicates with the interior chamber; and an exhalation valvecooperatively engaged to the housing in a manner wherein the valve pilotlumen is fluidly coupled thereto, the exhalation valve being fluidlycoupled to the interior chamber; the exhalation valve being piloted in amanner which facilitates the selective movement thereof from an openposition to which it is normally biased and wherein at least a portionof the interior chamber is vented to ambient air to a closed positionwherein fluid flow between the interior chamber and ambient air is atleast partially obstructed thereby.
 17. The nasal pillows mask of claim16 wherein the housing further defines a pressure sensing lumen whichfluidly communicates with the interior chamber.
 18. The nasal pillowsmask of claim 16 wherein the exhalation valve comprises a diaphragmwhich is movable between the closed and open positions.
 19. Theventilation mask of claim 16 wherein the exhalation valve at leastpartially resides within the interior chamber.